Duplicator and accompanying stencil carrier



Sept. 10, 1963 K. G. ZEUTHEN ETAL 3,103,167

DUPLICATOR AND ACCOMPANYING STENCIL CARRIER Filed Feb. 28, 1957 2 Sheets-Sheet 1 Fig.1

"' Fig.2

Fig.3

Sept. 10, 1963 K. ca. ZEUTHEN ETAL DUPLICATOR AND ACCOMPANYING STENCIL CARRIER Filed Feb. 28, 1957 2 Sheets-Sheet 2 United States Patent 3,103,167 DUPLICATOR AND ACCOMPANYING STENCIL CARRIER Karl Gustav Zeuthen, Gentofte, and Svend Hcnniug Geertsen, Kgs. Lyngby, Denmark, assignors to Zeuthen & Aagaard A/ S, Copenhagen, Denmark Filed Feb. 28, 1957, Ser. No. 643,123 Claims priority, application Great Britain Mar. 5, 1956 3 Claims. (Cl. 101-122) through which colouring paste, deposited in the rollers from one or several colour rollers, works out through the places where there are holes in a stencil laid on the silk screen. This screen must run synchronised with the duplioators main axle, which itself is driven either manually or by machine. Therefore, the construction must be such that no play exists between the driving duplicator roller and the roller of the driven stencil carrier.

A duplicator construction is known in which each of the two rollers have, on the ends along the circumference, evenly spaced, protruding, hemispherical studs, over which runs a spring-steel band containing holes corresponding to the studs, so that the band, which during operation lies around the roller, engages with these studs. The steel band serves as stencil carrier, and as a consequence of the hole-stud relationship, is forced to run in synchronisation with the driven duplicator roller, and thereby with the duplicators main axle.

The solution involving steel bands is, from the point of view of manufacture, an economical one, but the investigations underlying this invention, whose aim is to make the duplicator suitable for work at high speeds, have shown that difiiculties arise because steel bands have a tendency to break. With former normal speeds it has been possible to blame this breakage on flaws in manufacture, but with the increased speeds it is evident that there are such causes behind the occurring breaks that it would not be expedient to keep the existing construction merely with an eye to improvement of the quality of the steel bands since the inherent flaw lies in the use of this type of band.

Use of a stronger steel band would only increase the difiiculties, since investigation has shown that the trouble discussed here is due to severe tensions produced during the flexing to which the steel band is subjected when, in passing (from the straight-line portion of its course, it comes in against the rollers and is thereby bowed to their radius.

Experiment shows that cracks appear in the steel bands, radiating outward from the edges of the holes in them. Concentrations of pressure appear at these places, partly as a result of the very presence of the holes, with the resulting irregularity in the active area of cross-section and in the radii of curvature of the diiferent parts of the band, and partly because the studs in the \duplicators roller press against the edges of the holes. The indication seems to be to make such changes in the construction so that the stencil-bearing steel band is spared during operation. Theoretically there is the possibility oi increasing the diameter of the rollers, but this solution would in practice result in the machines becoming all too large in girth, and therefore the construction in question has been adhered to, and it has been decided until now to simply change bands as it becomes necessary.

3,103,167 Patented Sept. 10, 1963 The present invention provides a solution of this problem which has set a limit on the practical usable speed for duplicators with two or more duplicator rollers. The solution lies in using as a stencil carrier, at hand composed of flexible, elastic material, such as organic plastic (for example nylon), in which are inlaid extremely thin wires of steel, or other similar inextensi ble, but flexible material, which are twisted together.

In this manner it is achieved that only a very small part of the stencil carriers cross-section is composed of metal, and this metal is used in such a form that it can tolerate frequent bending and bowing without breaking. By virtue of their inextensibility the metal wires insure synchronisation between stencil and duplicating roller, and the fact that the remaining part of the band is composed of extensible material does not have any effect on precision, even at high speeds.

The invention is explained further in the following, by reference to the drawings, wherein:

FIG. 1 is a fragmentary plan View of a stencil carrier as presently used in duplicators;

FIG. 2 is a fragmentary plan view of the stencil carrier of the present invention;

FIG. 3 is a cross-sectional View taken on line 3--3 of FIG. 2;

FIG. 4 is a side elevational view of two duplicating rollers with the stencil carrier of this invention entrained thereon;

FIG. 5 is a fragmentary side elevational view of the stencil carrier with a stencil holder attached thereto;

FIG. 6 is a vertical cross-sectional view taken on line 66 of FIG. 5, and,

FIG. 7 is a top plan View of the holder and stencil carrier, as shown in FIG. 5.

The stencil carrier 1 shown in FIG. 1 is composed of a thin steel band and has circular holes .2 which pass down over hemispherical studs, for example, projecting out at regular intervals along the circumference of the duplioators rollers. Between these circular holes there are oblong openings 3, which serve to diminish the risk of breakage. The known stencil carrier involves two parallel-running bands lying at a distance from each other corresponding to the width of the stencil. These bands are endless, and run over (two duplicating rollers, one of which is driven synchronised with the main axle of the duplicator, whereas the other, which merely serves as undersupport, is mounted so as to turn freely.

The band 4, shown in FIG. 2, is endless and is made of nylon or of a similar flexible and durable material, and has on one side a row of equally spaced ribs 5, one of which is seen in FIG. 3. A completely flexible band is unsuitable as a stencil carrier inasmuch as the necessary synchronisation cannot be maintained by the aid of a band whose length changes during operation. In the hand itself, however, are inlaid Wires composed of thin steel threads twisted together 6, FIG. 3. In the cross-section shown are eight lengthwise-going wires, each composed of four thin strands twisted together into a single wire. Since the band is endless, a single strengthening wire wound up in spiral form with an appropriate number of turns can be used. The number of strands and wires, however, can be varied within wide limits, since the wires do not have to transfer forces of any considerable size, but simply insure that the flexible material of which the band is composed does not stretch and thereby give cause to synchronisation failure.

FIG. 4 shows two duplicating rollers 7 and 8, with a stencil carrier 4 as shown in FIG. 2. The part of the rollers or the discs connected to them, over which the appropriate part of the two-band stencil carrier runs, can have indentations for the ribs which are on the bands,

but it is also possible to use stulds which seat in holes in the bands, so long as it is insured that no slip occurs.

The side of the hand opposite to the rib-side can be, but does not have to be, smooth.

FIGS. 5, 6 and 7 show in different views a part of a stencil carrier according to the inventional. The stencil carrier is composed appropriately of two endless hands, of which only a part of one is shown and designated by '10. The band has on its underside a row of ribs 11 which act as synchronising elements, in that they seat in the corresponding indentations in the ends of the duplicators rollers. The two endless bands lie at a distance from each other corresponding approximately to the width of a stencil. v

Concerning the fastening of a stencil to the stencil carrier, there exists a stencil holder composed of a holder-part .12 having two locking tabs 13 and 14, see namely FIG. '6. The locking tabs 13 and 14 run from the upper side of the band through openings 15 and 16, so that parts of the locking tabs (in which openings 17 and 18, by preference round holes, are found) project through to the underside of the band. Through holes 17 and 18 is led a locking pin 19 containing a pair of notches 20 and 21, which set against the locking tabs 13- and 14 and serve to prevent locking pin 19 from being inadvertently displaced axially when first brought into position.

We claim:

1. In a duplicator of the type having parallel, spaced rollers, one of which is driven in a synchronized manner with the main axle of the duplicator and the other of which-is an idle roller; a stencil carrier comprising a pair of endless lbands entrained over the rollers and composed of flexible material inlaid with twisted (threads of flexible, inextensible material, said [bands being spaced 4 apart a distance approximately equal to the width of a stencil, said bands having ribs provided on their inner faces for engaging the rollers whereby the bands are positively entrained on the rollers to insure synchronization between the driving roller and the stencil, a stencil holder carried by the bands, said bands having transversely aligned and spaced apart openings formed therein, said holder having tabs extending through the openings to the inner fialces of the bands, said tabs having holes aligned transversely of the bands and a locking element fitted in the holes to lock the holder on the outer faces of the bands. 7

2. The combination of claim 1, wherein said ribs are formed in longitudinally spaced fiashion transversely on the inner faces of the bands, said holes passing through one of said ribs and said locking element extending axially of and disposed in the one of said ribs.

3. The combination of claim 1, wherein said ribs are formed in longitudinally spaced fashion transversely on the inner faces of the bands, said holes passing through one of said ribs and said locking element extending ax-ially of and disposed in the one of said ribs and means 10- cating said locking element against axial movement in said rib.

References Cited in the file of this patent UNITED STATES PATENTS 79 8,5 72 De Pew Aug. 29, 1905 1,205,315 Anthonyet al. Nov. 21, 1916 1,494,581 Breuer vet -al May 20, 1924 2,011,092 Uhl et all Aug; 13, 1935 2,019,375 Wheelwright Oct. 29, 1935 2,106,306 Putnam et al. Jan. 25, 1938 2,762,297 B'aer Sept. 11, 1956 

1. IN A DUPLICATOR OF THE TYPE HAVING PARALLEL, SPACED ROLLERS, ONE OF WHICH IS DRIVEN IN A SYNCHRONIZED MANNER WITH THE MAIN AXLE OF THE DUPLICATOR AND THE OTHER OF WHICH IS AN IDLE ROLLER; A STENCIL CARRIER COMPRISING A PAIR OF ENDLESS BANDS ENTRAINED OVER THE ROLLERS AND COMPOSED OF FLEXIBLE MATERIAL INLAID WITH TWISTED THREADS OF FLEXIBLE, INEXTENSIBLE MATERIAL, SAID BANDS BEING SPACED APART A DISTANCE APPROXIMATELY EQUAL TO THE WIDTH OF A STENCIL, SAID BANDS HAVING RIBS PROVIDED ON THEIR INNER FACES FOR ENGAGING THE ROLLERS WHEREBY THE BANDS ARE POSITIVELY ENTRAINED ON THE ROLLERS TO INSURE SYNCHRONIZATION BETWEEN THE DRIVING ROLLER AND THE STENCIL, A STENCIL HOLDER CARRIED BY THE BANDS, SAID BANDS HAVING TRANSVERSELY ALIGNED AND SPACED APART OPENINGS FORMED THEREIN, SAID HOLDER HAVING TABS EXTENDING THROUGH THE OPENINGS TO THE INNER FACES OF THE BANDS, SAID TABS HAVING HOLES ALIGNED TRANSVERSELY OF THE BANDS AND A LOCKING ELEMENT FITTED IN THE HOLES TO LOCK THE HOLDER ON THE OUTER FACES OF THE BANDS. 